Process for manufacturing microconduit networks formed by electrospinning techniques

ABSTRACT

A microconduit network structure and methods for making the same. One aspect of the invention relates to a microconduit network structure, including: a solid or semi-solid matrix having at least one interconnected web of filaments formed within the matrix; and wherein at least one interconnected web of filaments having diameters of about 10 nm to about 1 mm.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein may be manufactured and used by or forthe government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION

Embodiments of the invention generally relate to microconduit networks,and more specifically, microconduit networks formed by electrospunpolymer templates.

BACKGROUND OF THE INVENTION

From U.S. Pat. No. 6,858,057 “The term “electrospun fibers” isrecognized by those having ordinary skill in the art and includes thosefibers produced by the processes of U.S. Pat. No. 3,994,258 to Simm andU.S. Pat. No. 4,230,650 to Guignard. The processes provide methods toproduce fibers from either a molten polymer or a polymer in a solutionthat is drawn within an electrostatic field obtaining fine fibers of 2to 5 microns.”

Electrospun fiber mats have been used in the manufacture of contactlenses (U.S. Pat. No. 7,563,396), as porous scaffold media for cell andtissue growth (U.S. Pat. No. 6,592,623; U.S. Pat. No. 7,235,295; U.S.Pat. No. 7,531,503), as sensors and biosensors with high surface area(U.S. Pat. No. 7,264,762; U.S. Pat. No. 7,485,591), as field emittingelectrodes (U.S. Pat. No. 7,438,622), as porous and coating materialsfor implanted medical devices (U.S. Pat. No. 6,885,956; U.S. Pat. No.6,889,166; U.S. Pat. No. 6,889,374; U.S. Pat. No. 7,115,220; U.S. Pat.No. 7,244,272; U.S. Pat. Nos. 7,416,559 and 7,413,575), as staticdissipating media (U.S. Pat. No. 7,381,664), filters (U.S. Pat. No.6,743,273; U.S. Pat. No. 6,858,057; U.S. Pat. No. 6,924,028; U.S. Pat.No. 7,008,465; U.S. Pat. No. 7,070,640; U.S. Pat. No. 7,090,712; U.S.Pat. No. 7,090,715; U.S. Pat. No. 7,179,317; U.S. Pat. No. 7,192,434;U.S. Pat. No. 7,220,271; U.S. Pat. No. 7,290,672; U.S. Pat. No.7,270,693; U.S. Pat. No. 7,316,723; U.S. Pat. No. 7,318,852; U.S. Pat.No. 7,318,853), biodegradable absorbents (U.S. Pat. No. 7,172,765; U.S.Pat. No. 7,309,948), separators for batteries (U.S. Pat. No. 7,279,251),as electrodes for batteries and fuel cells (U.S. Pat. No. 7,229,944), asreinforcements (U.S. Pat. No. 6,265,333; U.S. Pat. No. 7,244,116), asmembranes (U.S. Pat. No. 6,800,155; U.S. Pat. No. 7,109,136), and ascatalyst beds (U.S. Pat. No. 6,916,758).

There are US Patents also involve polymer templating processes. U.S.Pat. No. 7,229,944 by Shao-Horn et al. describes how interconnectedelectrospun polymer fibers are used as a template for carbon fibersthrough graphitization processes, and how catalytic particles depositedinto the nanofibers subsequently grow to desirable sizes. The patentdoes not describe the use of electrospun fibers as templates for astructure with low yet continuous porosity.

U.S. Pat. No. 7,482,287 by Khatri et al. describes a templating processin which a polymer nanofiber is coated with a sol-gel ceramic,precursor. The polymer fiber is then removed and the result is a ceramicfiber of controlled diameter. The fibers so formed have no porosity, noris interconnection a key feature of the polymer template. The resultingprocess could not be used to form microconduit networks due to the lackof interconnection and the apparent compacting of the void formed byremoving the polymer.

U.S. Pat. No. 7,449,165 by Dai et al. describes a templating process forchromatographic columns in which structures having controlled micro- andmeso-porosity are formed by templating particles. These pores areinterconnected and the structure is mechanically robust, however, theporosity is not minimized while maintaining interconnection. Thus, themechanical properties are not optimal. For chromatography applications,the required pore volume is usually not minimized, in order to reducethe overall size of the column.

U.S. Pat. No. 7,419,772 by Watkins et al. describes a templating processinvolving block copolymers. However, a fully interconnected structurewould require a porosity in easily in excess of 20 vol % due to thefeatures of ordered block copolymer geometry. U.S. Pat. No. 7,190,049discloses a similar method for producing arrays of nanocylinders. Thesearrays do not involve extensive interconnection between individualcylinders. U.S. Pat. No. 7,189,435 describes a similar process incombination with lithographic techniques. The porosity in such astructure would not be homogeneously distributed. The resultantinhomogeneity would typically lead to inferior mechanical properties.

U.S. Pat. No. 7,345,002 by Schaper disclosed a method for replicatingpolymer microstructures. All such replication and transfer methods (see,for example, U.S. Pat. No. 6,849,558) involve surface topography only,and cannot be used to product a fully three-dimensional network ofembedded pores. U.S. Pat. No. 7,186,355 by Swager describes compositionsinvolving nanoscopic pathways. These pathways are not hollow and, thoughthey can conduct ions or electrons, cannot transport nanoparticles, norcould they transport fluids rapidly.

There are patents involving photonic crystals and/or ordered nanoporearrays. These involve templating with close packed polymer structures(needed to create the regular array) and therefore involve a much higherlevel of porosity. U.S. Pat. No. 6,929,724 (in addition to numerousother patents and publications, for example U.S. Pat. No. 6,649,083)disclose methods for creating porous structures using colloids astemplates. Colloidal templates usually produce non-interconnected poresunless the porosity is greatly in excess of 20 vol %. The sparse,interconnected, highly branched network templates formed by electrospunfibers are not stable geometries for known colloidal materials. The samedistinctions apply with respect to numerous patents involving lyotropicliquid crystalline materials used during templating processes.

U.S. Pat. No. 6,176,874 discloses the use of solid free-form fabricationtechniques such as Stereolithography (SLA), selective laser sintering(SLS), ballistic particle manufacturing (BPM), fusion depositionmodeling (FDM), and three dimensional printing (3DP) to form vasculartemplates having a the characteristics of electrospun fiber templates.These techniques are limited in the spatial resolution of structuresthat may be produced in a practical time period, and would generally beunsuitable for continuous production of microconduit network structures.

U.S. Pat. No. 5,522,895 describes a method of using a porous butmechanically strong template for the purpose of growing bone. Theporosity is explicitly stated to be from 20% to 50% (by volume), theporosity is gradually replaced by living tissue, thereby aiding in thelong-term retention of mechanical properties, and the strength andstiffness of the system are specified in terms of exceeding an absolutethreshold, rather than being near optimal.

Despite the wide variety of patents cited above, there is no knownpatent or publicly available literature that describes any embodimentbelow, compatible with high-speed mass production, for fabricating amicroconduit network structure, that is, a series of highlyinterconnected pores or channels in which the total volume fractionoccupied by pores is on the order of 10% or less. The low porosity ofthe microconduit network structure combined with the small diameter ofthe pores provides for significant benefits in the mechanical propertiesof porous structures while permitting the rapid transport or circulationof fluids within the structure.

It is to be understood that the foregoing is exemplary and explanatoryonly and are not to be viewed as being restrictive of the invention, asclaimed. Further advantages of this invention will be apparent after areview of the following detailed description of the disclosedembodiments, which are illustrated schematically in the accompanyingdrawings and in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-C are cross-sectional views of the microconduit template FIG.1A, shown as embedded in structure FIG. 1B, and shown after extractionFIG. 1C, according to embodiments of the invention.

FIG. 2 is a lateral view of an electrospinner orifice using electrifiedjets of polymer to form unstable filaments of polymer solution on aground lane and/or carrier substrate, according to embodiments of theinvention.

FIG. 3 is a side view of an embodiment of the invention illustrating theworkings a producing an MCN, according to embodiments of the invention.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not to be viewed as being restrictive of the invention, as claimed.Further advantages of this invention will be apparent after a review ofthe following detailed description of the disclosed embodiments, whichare illustrated schematically in the accompanying drawings and in theappended claims.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

Embodiments of the invention relates to microconduit network structuresand methods for making the same. An aspect of the invention relates to aprocess for manufacturing microconduit network structures, including:providing a set of electrospinning orifices associated with an effectiveamount of solution; maintaining the orifices at a desired voltage to agrounding plane; inducing opposite electrical charges from the voltageto electrify jets of the solution and the jets of solution accelerate toand on the grounding plane transforming the solution into branched websof filaments; depositing at least one interconnected branched webs offilaments on a carrier substrate; dispensing the solution; adding amatrix precursor fluid into the branched webs of filaments from thedispensing mechanism: solidifying the matrix fluid; and extracting orremoving the branched webs of filaments from the matrix.

Another aspect of the invention relates to a microconduit networkstructure, including: a solid or semi-solid matrix having at least oneinterconnected web of filaments formed within the matrix; and wherein atleast one interconnected web of filaments having diameters of about 10nm to about 1 mm. Other aspects of the invention relates to an apparatusto manufacture microconduit network structures, including: at least onemechanism having a set of electrospinning orifices to expel an effectiveamount of solution; at least one ground plane, wherein the orifices aremaintained at a desired voltage to the grounding plane; a device thatinduces opposite electrical charges from the voltage to electrify jetsof the solution and the jets of solution accelerate to and on thegrounding plane transforming the solution into branched webs offilaments; at least one carrier substrate, wherein a mechanism depositsat least one interconnected branched webs of filaments on a carriersubstrate; at least one dispensing mechanism; at least one matrixprecursor fluid added into the branched webs of filaments from thedispensing mechanism; a device to solidify the matrix fluid; and adevice that extracts or removes the branched webs of filaments from thematrix.

In embodiments of the invention, when the solution is utilized, itincludes at least one of a polymer and at least one solvent. Inembodiments, the solution includes at least polystyrene. Embodiments ofthe invention include, but not limited to, a matrix having a liquidnon-solvent monomer. In other embodiments, the matrix includes, but isnot limited to, at least one of thiol-enes (NOA81), ceramic precursor,metal-filled polymer, cyanate ester, acrylates, and silicones, andepoxies.

There are a variety of ways to extract or remove the matrix. Embodimentsof the invention include, but are not limited to, the use of solvent(s),radiation, and/or heat depending on matrix and filament materialsutilized. Embodiments of the invention include the matrix beingsolidified by a curing step. In other embodiments, the process furtherincludes passing the webs by a dam. Still yet other embodiments furtherinclude at least one metering blade to control thickness of the liquidlayer encapsulating the webs and to provide minimum of air entrapmentwherein the matrix is solidified by a curing step. Of course themicroconduit network structures produced by the process described inthis application are other embodiments of the invention.

In embodiments, the interconnected web of filaments have diameters ofabout 10 nm to about 1 mm or 1000 nm to 1 mm. In other embodiments, theinterconnected web of filaments have diameters ranging from about 900 nmto about 1 mm. Yet in other embodiments, the diameters range from about100 nm to about 0.01 mm. In other embodiments, the process includes atleast one dam to pass said webs by a dam. In other embodiments, theprocess includes at least one metering blade to control thickness of aliquid layer encapsulating said webs and to provide minimum of airentrapment. In other embodiments, the solution includes at least onepolymer and at least one solvent. In other embodiments, the solutionincludes at least polystyrene.

The invention addresses the problem of incorporating a micro-porousnetwork (an interconnected series of micron-sized channels) into astructural material, simultaneously maintaining 1) minimal overallporosity, which leads to minimal loss in strength and stiffness, and 2)maximum interconnectivity of the channels, which enables efficienttransport of functional molecules and/or nanostructures within thesystem.

Step-by Step Description and Explanation of Embodiments of theInvention:

Embodiments of the invention include a microconduit network embeddedwithin a solid matrix material and the method for producing a network atlarge scale continuously. The network is formed by electrospinningpolymer solutions into a fibrous web with the special characteristicthat most filaments share a branching connection to at least two otherfilaments, thereby forming a continuously connected network encompassingmany filaments. The filament network serves as a template for themicroconduit network. Once deposited, the filament network isencapsulated in a liquid matrix precursor material. The precursor may bepolymeric (thermally or UV cured), ceramic, or liquid metal. Theencapsulated filaments are then conveyed through a curing station, wheretemperature and/or UV radiation is used to convert the liquidencapsulant into a solid encapsulant. After passing through the curingstation, the solid is washed with a solvent for the polymer filaments.Upon exposure to the solvent, the polymer filaments are dissolved awayleaving behind a network of interconnected channels within the solidmatrix. This arrangement is termed a microconduit network since thefilaments are approximately micron-sized and form an interconnectednetwork. The network is then sealed by placing removable protectivefilms on either side. As formed, the material is capable of absorbingfluids laden with functional chemicals or nanoparticles by capillaryaction. The functional chemicals or nanoparticles may be altered at willby a procedure of flushing and refilling with any combination of fluidsor nanoparticles.

A micro-porous network within a structure can act as a type of embeddedcirculatory system, enabling the transport throughout the structure ofmolecules and/or nanostructures that may be constructed and/orformulated to perform various functions, including, but not limited to,imparting camouflaging characteristics, monitoring the structure forevidence of chemical and biological attack, determining the extent ofcorrosion or fouling nearby the structure, receiving and transmittingelectromagnetic signals, harvesting solar energy, producing orchemically converting fuels and other valuable liquid substances, ormonitoring the health of individuals through contact with biologicalfluids. The functional molecules and/or nanostructures can not only betransported within the network, they may be patterned or re-patternedthrough the application of external magnetic fields, gravitational orcentrifugal forces, or exposure to incident electromagnetic radiation.

In addition, the functional molecules and/or nanostructures may besupplied or re-supplied from an external store that is attached to thenetwork from time to time, or they may be removed from the network by awashing process using an external store of fluid that is connected tothe network from time to time. The ability to introduce or removetailored sets of functional molecules and/or nanostructures provides thesystem with the characteristic of adaptive multi-functionality, that is,the functions that the system may perform can be altered at will. Theability to change the functionality of an object at will has been animportant characteristic of systems, including desktop computer(laptops), or more recently, cellular telephones (smart phones), thatexhibit rapidly increasing capabilities and rapidly decreasing costs ofoperation over time. By introducing similar capabilities into structuralmaterials, similar rapid gains in functional capability and decreasingoperational costs may be realized. The availability of these materialswould enable the resultant systems to gain a rapid adaptationcapability, which is presently absent in virtually all common structuralmaterials.

A micro-porous network with the characteristics of an efficientcirculatory system (minimal occupied volume of transport conduits,maximum rates of transport, and maximum penetration of conduits into thesurrounding volume) is a complex structure. To fabricate a structure atthe micron scale using conventional machining techniques would beextremely expensive and time-consuming. On the other hand, porousstructures that are formed by other methods (often involvingself-assembly or embedding of continuous template structures) typicallyinvolve features generated by numerous stochastic processes leading tointerconnection patterns characterized by randomness. As a result,porous structures formed by these methods in which the pores occupy lessthan about 20% of any given volume tend to have few connections betweenpores, giving rise to poor transport characteristics. Since higherporosity almost always leads to substantial decreases in the strengthand stiffness of structures, there is typically a highly constrainingtrade-off between the efficiency of transport and the loss of mechanicalproperties in porous structures formed by other processes.

Embodiments of the invention effectively circumvents the above trade-offby relying on the characteristics of electrospun fibers as porogens toproduce a template structure that has a high degree of interconnectivitybut a low occupied volume fraction. When a porous structure is producedby embedding the template in a matrix and then removing the template,the result is an interconnected network of micro-pores having a lowoccupied volume fraction. NAWCWD laboratory notebooks include all testresults and data describing results of embodiments of the invention.

Another embodiment of the invention includes an example of amethod/process embodiment include:

-   -   Turn on conveyor belt.    -   Turn on washing fluid removal system.    -   Turn on curing system.    -   Begin dispensing matrix precursor and washing fluids.    -   Begin dispensing protective film.    -   Apply voltage to electrospinner orifice.    -   Adjust metering blades, dispensing rates, electrospinning        parameters, and curing system parameters as needed.    -   Begin collecting product.    -   Adjust all process parameters and refill fluid containers as        necessary.

To shut down,

-   -   Stop collecting product    -   Adjust metering blades, dispensing rates, electrospinning        parameters, and curing system parameters as needed.    -   Ramp applied voltage to zero (relative to ground plane) at        electrospinner orifice.    -   Stop dispensing matrix precursor fluid.    -   Turn off curing system after last fluid has passed through and        cured.    -   Stop dispensing protective film when last solid matrix passes by        dispensers.    -   Stop dispensing wash fluid.    -   Turn off vacuum when last washing fluid has been collected.    -   Turn off conveyor belt.

As shown in FIGS. 1A-C, 2, and 3, at least one electrospinning orifices18 are/is associated with the reservoir of a polymer solution (example:20 wt % polystyrene in toluene). The orifice(s) 18 are maintained at avoltage between 100 V and 100 kV relative to a grounding plane 24. Thehigh voltage induces opposite electrical charges to accumulate on theground plane 24 and on the tip of a fluid jets 20 that emerge from theorifices 18. Driven by the attractive force between the oppositeelectrical charges, the jets 20 accelerate towards the ground plane 24.The rapid motion of the jets 20 causes rapid evaporation of the solventwithin them, leading to a decrease in the diameter of the jets 20, aprocess aided by the phenomenon of stable necking associated withaccelerating fluids. As the diameter of the jets 20 becomes decreases tounder 100 micrometers, repulsive forces between like charges at the tipsof the jets 20 causes each jet to become mechanically unstable and tofragment into sub-jets 22 that accelerate away from one another. The subjets 22 then undergo a cascading fragmentation process, producing abranching pattern of fluid jets 22 with increasingly small diameter. Thedecreasing diameter further accelerates the drying process within eachsub-jet, resulting in the formation of a solid filament of microscopicdiameter. Because these filaments form from a substantially continuouslybranching network (there can be a fraction of a break) of fluid jets,they do not become completely separated one from another and some canjoin/mold/fuse together. Rather, as they reach the ground plane 24, theyaccumulate as a loose pile of dried filament webs 26. These piles ofwebs form a highly entangled series of interconnected filament networks.Electrospinning of polymer solutions has been described in detail innumerous publications for one skilled in the art to review which can beutilized in embodiments of the invention.

As shown in FIG. 3, the ground plane 24 forms part of a conveyor belt,which continuously removes the dried filament web 26 at a predeterminedrate. This web serves as the soluble template for the microconduitnetwork. The web then passes under a dam 28 and a dispenser for thematrix precursor fluid 30. The web then passes under a metering blade 32that controls the thickness of the liquid layer encapsulating the web.The construct of the dam 28, dispenser 30, and metering blade 32 is suchthat encapsulation of the web is achieved with a minimum of airentrainment, a feature readily attainable to those skilled in the art.The precursor fluid dispensed by the dispenser 30 is of such a naturethat it may be readily solidified, either by the application of heatcausing a thermochemical cross-linking reaction (example, the dicyanateester of bisphenol E catalyzed with 3 parts per hundred by weight ofnonylphenol and 0.12 parts per hundred by weight of cobalt(II)acetylacetonate), the application of UV radiation leading tocross-linking (example, Norland Optical Adhesive NOA81, a commerciallyavailable thiol-ene-based system), or the application of cooling leadingto freezing (example, polyethylene glycol). However, depending on thematrix materials utilized, other solidifying techniques can be used. Theconveyor belt is then passed through an apparatus 34 consisting of achamber in which the temperature and/or radiation fields of a controllednature sufficient to achieve solidification within the residence time ofthe material on the conveyor belt.

Within this apparatus, there may be exhaust units 36 supplied for thepurpose of removing byproducts of the solidification process. Theencapsulated web 38 then exits the apparatus 34 as a solid slab ofmaterial with an embedded network of soluble polymer filaments. Awashing fluid dispenser 40 then dispenses a solvent that can selectivelydissolve the polymer filaments (example toluene for polystyrene), whichcomes into contact with the filaments. The dispensing apparatus 40 mayinclude a cutting system for breaching the solid encapsulant in order tofacilitate such contact. As contact with the solvent continues, thesolid matrix 42 remains in-tact while encapsulating a web of liquidsolution rather than a web of solid filaments, as the filamentsdissolve. The conveyor then passes through a vacuum or other collectionsystem 44 that forces the polymer solution out of the channels that haveregions where the solid filaments once existed. The conveyor belt thenpasses under a dispenser 46 that introduces a protective film over thesolid slab with a network of microscale conduits (herein referred to asa microconduit network). The side of the film that contacts the networkmay be coated with a removable adhesive, and/or with a fluid mixture,possibly having dispersed solid or liquid nanoparticles that canpenetrate into the channels. The conveyor now carries a microconduitnetwork 48 with a selected fluid possible introduced and one protectivefilm cover. Through a series of contact rollers or other apparatusavailable to one skilled in the art, the uncoated side of themicroconduit network is exposed and passed next to a second dispenser 50that applies a protective film. As with the previously appliedprotective film, the side contacting the microconduit network may becoated with an adhesive and/or a penetrant fluid. Once applied, thefinal product(s) 52 of the microconduit network, with up to at least twopenetrant fluids, coated on both sides by a removable protectivebarrier, is collected.

Variations on the aforementioned process easily produced by one skilledin the art could include the introduction of more than two types ofpenetrant fluid, introduction of multiple protective and/or adhesivelayers, production of multi-layer microconduit network systems,production of microconduit networks in specifically defined spatialregions of a multi-component and/or multi-layer slab, cutting, stacking,separating, and/or adhering the slabs, in conjunction with possibleadjustments to the solidification process, in order to create amicroconduit network of any desired shape intermingled with a solid orfluid of any other desired shape, control of the diameter and density ofthe fibers comprising the template for the microconduit network, the useof multiple template materials, and the use of spatially selectivefilling processes.

One skilled in the art could also readily carry out operationsincluding, but not limited to, flushing the microconduit network toremove a fluid or nanoparticle mixture, introduction of new and varyingfluid and/or nanoparticle mixtures at will, combining of multiple fluidand/or nanoparticle mixtures, including combination with such mixturespreviously existing within the network to create new mixtures, treatmentof the surfaces of the walls of the conduits so as to favor introductionand transport of fluid and/or nanoparticle mixtures to within definedspatial regions of the network, blocking of the channels by introductionof particles with a pre-defined diameter falling within the range of thechannel diameters, stretching of the matrix in conjunction with the useof elastically pliant matrix materials so as to alter the size and shapeof conduits within the network, and/or manipulation of nanoparticleswithin the channels through the use of magnetic fields, directed beamsof penetrating radiation, hydrostatic pressure fields, and/or dynamicmechanical fields (including ultrasonic acoustic pulses).

Embodiments of the invention have application to, but not limited to,re-configurable conformal antennas, re-configurable chemical andbiological sensors, structural fuel storage and treatment, structuralbatteries, embedded photovoltaic devices, active camouflage, embeddedcomputing, structural health monitoring, physiological healthmonitoring, embedded information displays, self-healing structures,chemical and biological decontamination equipment, chemical andbiological protective equipment, and bandages.

The following prophetic examples are for illustration purposes only andnot to be used to limit any of the embodiments. Embodiments of theinvention include, but are not limited to, the following examples andranges for Electrospun fiber MCN.

Examples of polymers that could be dissolved and electrospun intotemplates from solution include low density polyethylene, atacticpolypropylene, polyvinyl chloride, polystyrene, substituted polystyrenesincluding poly-(alpha-methyl)styrene, polyamides including Nylon 6,6,Nylon 4,10, Nylon 6,10, Nylon 6,12, and proteins, cellulose andchemically modified cellulosic materials including cellulose acetate,poly(vinyl acetate), and polyesters including polyethyleneterephthalate. Other materials utilized in embodiments of the inventioninvolve polymers with good solubility in organic solvents, amorphous orslightly crystalline polymers, and polymers with low thermal stability.Yet other materials utilized include a molecular weight distributionthat facilitates the electrospinning process by conferring mechanicalstability to rapidly drawn and evaporated solutions at concentrationstypical of the electrospinning process.

Examples of solvents that could be employed in the electrospinningprocess include pentanes, hexanes, heptanes, benzene, toluene, xylenes,ethylbenzene, acetone, methyl ethyl ketone, cyclopentanone,cyclohexanone, diethyl ether, tetrahydrofuran, isopropanol, n-butanol,n-pentanol, n-hexanol, ethylene glycol, propylene glycol, ethyleneglycol diethyl ether, glycerol, dimethyl acetamide, dimethyl formamide,1-methyl-2-pyrrolidone, dimethyl sulfoxide, anisole, veratroloe,cyclohexane, versions of these aforementioned wherein one or morehydrogen atoms is replaced by a F, Cl, or Br atom, and versions ofn-propane, n-butane, and isobutene in which one or more hydrogen atomsis replaced by a F, Cl, or Br atom. Other solvents have a moderate vaporpressure at room temperature to 100° C. and are of low reactivity. Inother embodiments of the invention, the electrospinning and rinsingsolvents will be of the same or similar composition.

Examples of matrix materials include, but are not limited to, epoxy,cyanate ester, phthalonitrile, thermosetting polyimide, thermosettingpolyester, phenolic, bismaleimide, and thiol-ene polymers, silica,titania, alumina, or other condensable ceramics, low melting pointmetals such as lead, castable or powdered metal or ceramic particleswith polymeric binders, or other free-flowing material compositionscapable of penetrating micron-sized regions. Examples of liquids addedto the microconduits include, but are not limited to, water, dimethylformamide, 1-methyl-2-pyrrolidone, ethylene carbonate, propylenecarbonate, naphthalene, mineral oil, silicone oil, diphenyl ether, orother non-volatile liquids, any of the solvents listed previously, orany combination thereof.

Examples of functional molecules incorporated into the microconduitsinclude dyes colorants, reactive monomers, chemical sequestrationagents, fluorescent markers, lipids, proteins, biocides, clottingagents, detergents, and surfactants (including, but not limited toCoumarin and Rhodamine). Examples of nanoparticles incorporated into themicroconduits include functionalized or unfunctionalized silica,alumina, titania, gold, silver, zeolites, graphites, boron nitride,silsesquioxanes, fullerenes, cobalt, and iron oxide (eg. hematite),amorphous or of any practically attainable crystal polymorph, and in anycombination including particles with multiple chemical and/or crystalpolymorph components. Electrospinning, conveyor belt, curing, rinsing,and any needed drying steps are carried out at temperatures (typically20-100° C. for all steps except curing, which may range from 20-300° C.,with a possible range of −200-200° C. for all steps except curing, and−20 to 400° C. for curing, and required voltage levels (typically1000-10,000 V, but ranging from 100 to 100.000 V), polymerconcentrations (typically 5-25 vol %, but possibly 0.1-100 vol %, thepolymers can be molten rather than in solution), and conveyor speeds(typically 10 cm/min-100 cm/min, but possibly 0.1 cm/minute to 10,000cm/min), film thicknesses (typically 0.1-1 mm, but possibly 0.001 mm-100mm), determined using methods familiar to one skilled in the art. Theprocess may involve typically 1-10 electrospinning orifices, but couldinvolve 1-10,000 orifices, and a line width of typically 5-50 mm butpossibly 0.1 mm-10,000 mm.

The process could be a continuous or a batch process. Necessaryproduction machinery, packaging, finishing, refilling, and othermaintenance operations can be added as determined by one skilled in theart. Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassedwithin the invention. The upper and lower limits of these smaller rangesmay independently be included or excluded in the range, and each rangewhere either, neither or both limits are included in the smaller rangesis also encompassed within the invention, subject to any specificallyexcluded limit in the stated range. Where the stated range includes oneor both of the limits, ranges excluding either or both of those includedlimits are also included in the invention.

While the invention has been described, disclosed, illustrated and shownin various terms of certain embodiments or modifications which it haspresumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims here appended.

1. A process for manufacturing microconduit network structures,comprising: providing a set of electrospinning orifices associated withan effective amount of solution; maintaining said orifices at a desiredvoltage to a grounding plane; inducing opposite electrical charges fromsaid voltage to electrify jets of said solution and said jets ofsolution accelerate to and on said grounding plane transforming saidsolution into branched webs of filaments; depositing at least oneinterconnected branched webs of filaments on a carrier substrate;dispensing a matrix precursor fluid into said branched webs offilaments; solidifying said matrix fluid; and extracting or removingsaid branched webs of filaments from said matrix.
 2. The processaccording to claim 1, wherein said solution comprises of at least onepolymer and at least one solvent.
 3. The process according to claim 2,wherein said solution comprises of at least polystyrene.
 4. The processaccording to claim 1, wherein said matrix is a liquid non-solventmonomer.
 5. The process according to claim 1, wherein said matrixcomprises at least one of thiol-enes (NOA81), ceramic precursor,metal-filled polymer, cyanate ester, acrylates, and silicones, andepoxies.
 6. The process according to claim 1, wherein said step ofextracting or removing said matrix includes the use of heat.
 7. Theprocess according to claim 1, wherein said step of extracting orremoving said matrix includes the use of solvents.
 8. The processaccording to claim 1, wherein said step of extracting or removing saidmatrix includes the use of solvent(s), radiation, and/or heat dependingon matrix and filament materials.
 9. The process according to claim 1,wherein said matrix is solidified by a curing step.
 10. The processaccording to claim 1, further comprising passing said webs by a dam. 11.The process according to claim 1, further comprising metering blade tocontrol thickness of the liquid layer encapsulating said webs and toprovide minimum of air entrapment wherein said matrix is solidified by acuring step.